xeos
/
num-traits
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

bigint::monty: use mac_digit

This commit is contained in:
Josh Stone 2017-10-22 15:30:17 -07:00
parent 4d35815426
commit 5a0de140c9
2 changed files with 2 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
bigint/src/algorithms.rs
View File

@ -220,7 +220,7 @@ pub fn sub_sign(a: &[BigDigit], b: &[BigDigit]) -> (Sign, BigUint) {
/// Three argument multiply accumulate:
/// acc += b * c
fn mac_digit(acc: &mut [BigDigit], b: &[BigDigit], c: BigDigit) {
pub fn mac_digit(acc: &mut [BigDigit], b: &[BigDigit], c: BigDigit) {
if c == 0 {
return;
}

18
bigint/src/monty.rs
View File

@ -73,27 +73,11 @@ fn monty_redc(a: BigUint, mr: &MontyReducer) -> BigUint {
// 1: for i = 0 to (n-1)
for i in 0..n_size {
// Carry storage
let mut carry = 0;
// 2: q_i <- mu*c_i mod β
let q_i = ((c[i] as u64) * mu) & beta_mask;
// 3: C <- C + q_i * N * β^i
// When iterating over each word, this becomes:
for j in 0..n_size {
// c_(i+j) <- c_(i+j) + q_i * n_j
let x = (c[i+j] as u64) + q_i * (n[j] as u64) + carry;
c[i+j] = (x & beta_mask) as u32;
carry = x >> 32;
}
// Apply the remaining carry to the rest of the work space
for j in n_size..2*n_size-i+2 {
let x = (c[i+j] as u64) + carry;
c[i+j] = (x & beta_mask) as u32;
carry = x >> 32;
}
super::algorithms::mac_digit(&mut c[i..], n, q_i as u32);
}
// 4: R <- C * β^(-n)